With a screen resolution of 1440x900, you don't need a great deal of graphics power. And certainly don't need crossfire or sli . . . even if you plan to move up past 1680 resolution to 1920.
For gaming at 1920 resolution, an i5 750 coupled with a HD6850 or a GTX460 depending on pricing from vendors you can access. Motherboard from Asus or Gigabyte.
Power Supply: The psu is more important than most people realize. Do not buy a cheap bargain unit. Please stick with brands like Seasonic, Corsair, XFX, PC Power & Cooling if you can. A 450-550W psu is plenty for one video card, a 650-750W should be used if you want to allow for crossfire/sli.
Memory: You need not buy memory faster than 1333, CL9. If you can get memory with latency 8 or 7 (instead of 9) for very little more money, that's fine. But you will not notice any difference in gaming due to faster memory.
HD: Here the Samsung Spinpoint F3 500GB or 1TB is the drive of choice.
If you give me a site I can access and that you can buy from, I'd be happy to pull together specifics.